Input devices are the hardware that give computers instructions. Output devices relay the response from the computer in the form of a visual response (monitor), sound (speakers) or media devices (CD or DVD drives). The purpose of these devices is to translate the machine's response to a usable form for the computer user.
Video Card and Monitor
The video card and monitor work in conjunction to display visual output for the user. These two hardware devices help the user return instructions to the computer as well. The video card processes the images seen on the monitor. Monitor and video card quality determine how detailed images are returned. For users who only use a computer for data entry or office work, the images aren't as detailed. Gamers use the output of a video card and monitor to display detailed, 3D images, so the output instructions are more advanced.
Sound Card and Speakers
Although a monitor and video card are required components for a computer, a sound card and speakers are optional. However, these two output devices give a better user experience for the computer. Just like a monitor and video card, the quality of the hardware output devices for sound also determine the detail. Speakers and sound card can provide surround sound just like a television setup. This type of sound setup is used by gamers and multimedia creators. There are also headsets available for speakers, so the output can be heard by the computer users without disturbing others in the home.
CD and DVD Media
Writable CDs and DVDs have become a standard output device for computers. A hard drive stores information, and it's a required component. However, a CD or DVD is optional. The advantage of these hardware devices is storing data for a long period of time. CDs and DVDs are also used to share information with others. Users write data to a CD or DVD and store it in a location in case of a hard drive crash, of if an important document is accidentally deleted. CDs can be used in cars or portable devices to listen to music downloaded from software such as iTunes.